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你能帮我吗？猫的图像没有显示在画布上。我不知道我的代码是什么错误。画布有问题
HTML：
<html>
<head>
<link type="text/stylesheet" rel="stylesheet" href="style.css" />
</head>
<body>
<center>
<h1>Little Cat</h1>
<canvas id="main" height="300" width="300"></canvas>
</center>
<script type="text/javascript" rel="javascript" src="script.js">Try another browser</script>
</body>
</html>
的Javascript：
var canvas = document.getElementById('main'),
ctx = canvas.getContext('2d');
var catI = new Image();
catI.src = "Image/cat.gif";
function Cat(x, y){
this.x = x || 20, this.y = y || 50, this.img = catI, this.speed = 3, this.keyInput = {};
this.display = function(){
//control movements
if(this.keyInput[38] === true){
this.y -= this.speed;
}
if(this.keyInput[40] === true){
this.y += this.speed;
}
if(this.keyInput[37] === true){
this.x -= this.speed;
}
if(this.keyInput[39] === true){
this.x += this.speed;
}
else{
this.x += 0;
this.y += 0;
}
//stay within the canvas
if(this.x < 0){
this.x = 0;
}
if(this.x > canvas.width - 50){
this.x = canvas.width - 50;
}
if(this.y < 0){
this.y = 0;
}
if(this.y > canvas.height - 50){
this.y = canvas.height - 50;
}
ctx.drawImage(catI, this.x, this.y);
};
}
var cat = new Cat(50, 50);
document.addEventListener("keydown", function(e){
cat.keyInput[e.keyCode] = true;
});
document.addEventListener("keyup", function(e){
cat.keyInput[e.keyCode] = false;
});
function animate(){
cat.display();
}
window.requestAnimationFrame(animate);